STAURASTRUM. 135 



the base of each process. These are not very distinct in 

 PL CXLIX, fig. 12, but can be recognised in fig. 1, PL CLXVI. 



135. Staurastrum cyrtocerum Breb. 

 (PL CXLIX, fig. 9 ; PL CL, fig. 4.) 



~<t lurastrum cyrtocerum Breb. in Ralfs, Brit. Desm. 1848, p. 139, t. 22, f. 10 ; 

 Arch, in Pritch. Infus. 1861, p. 742 ; Rabenh. Krypt.-fl. Sachs. 1863, 

 p. 191 ; Wittr. Gotl. Ol. sotv. Alg. 1872, p. 51 ; Wolle, Desm. U. S. 

 1884, p. 128, t. 42, f. 30, 31 ; Cooke. Brit. Desm. 1887, p. 168, t. 58, f. 3 ; 

 De Toni, Syll. Alg. 1889. p. 1207 ; West, Ale. X. Wales, 1890, p. 18, f. 16 ; 

 Alg. W. Ireland, 1892, p. 181 ; Alg. Engl. Lake Distr. 1892, p. 20 ; Roy 

 A: Biss. Scott, Desm. 1893, p. 19 ; Comere, Desm. de France, 1901, p. 155, 

 t. 11, f. 17; W.^t \ <;. S. West, Alga-fl. Yorks. 1902, p. 104; Alg. N. 

 Ireland, 1902, p. 53 ; Borge, in Botan. Xotiser, 1913, p. 32. 



Phycastrum cyrtocerum Kiitz. Spec. Alg. 1849, p. 180. 



JStaurastrum polymorphism var. cyrtocerum Rabenh. Flor. Europ. Alg. 1868, 

 p. 210. 



Cells rather under medium size, usually somewhat 



/ 



broader than long, including the processes, deeply con- 

 stricted, sinus rectangular, acute ; semicells cup-shaped, 

 ventral margin very tumid, dorsal margin convex, often 

 with a row of minute emarginate granules visible, espe- 

 cially in slightly tilted specimens, upper angles produced to 

 form short stout converging processes, gradually tapering 

 towards their apices, which are tipped with 2 or 3 minute 

 spines ; cell-wall rough with minute granules, arranged 

 in concentric series round the angles, and in longitudinal 

 rows across the face of the semicell, median row incom- 

 plete ; cells often twisted about the isthmus. Vertical 

 view triangular or quadrangular, sides concave, with a 

 TOW of minute emarginate granules just within each 

 lateral margin; angles produced into short processes, 

 which are often abruptly bent, all in one direction. 



Zygospore orbicular, with spines slightly forked at the 

 apex (Ralfs). 



Length 23-39 [JL ; breadth, including processes, 33- 

 60 [i ; breadth of isthmus 8-11 [i. 



ENGLAND. Cumberland ! Westmoreland ! X. and 

 H. Yorks ! Cheshire (Roy). Burnham Beeches, Bucks ! 

 Gloucester (Ralfs). Surrey! Sussex (Ralfs). Hants'. 

 i>3von! (Harris). Cornwall! 



